Nanoscale devices for controlled fluid handling and cell interrogation have attracted a great deal of interest recently. Microfluidics led to major advances in biology and medicine, permitting DNA sequencing and breakthroughs in medical diagnostics. Further progress will require a million- to billion-fold reduction in the volume of fluid samples to the level of attoliters, which will enable probing of individual cells and intracellular organelles. On a single-cell level, glass micropipettes are employed for cellular injection and recovery applications ranging from therapeutic cloning to pharmacology. Difficulties, such as membrane rupture, inaccurate transplant, and fatal damage of crucial organelles, are often encountered using these capillaries to study single cells. Sharpened tubules formed by quartz capillary pulling, usually called “nanopipettes”, can be drawn to ca. 25 nm. However, they bend and break easily. Therefore, the size is limited for practical reasons, and glass pipettes with tip diameters less than 500 nm are rarely used in practice. Targeting of the nucleus in fairly large cells (e.g. oocytes) is possible with glass pipettes, but specific organelles cannot be injected into or analyzed using the current technology.
Carbon nanotubes may also be used to interrogate or deliver payloads to cells. Such probes appear to offer significant advantages over sharpened glass micropipettes. But present methods of producing probes based on such nanotubes are limited.